(1) Field of the Invention
The present invention relates to a barrel cylinder for a plastic writing instrument which has, at its distal end, a distal end port of the barrel cylinder where a writing element extends, and which is injection-molded.
(2) Description of the Prior Art
When a barrel cylinder for a writing instrument is injection-molded with a plastic, the mark of the gate of the mold, i.e., a gate mark, appears on the product. If the gate mark appears on the surface of the product, the appearance of the product becomes poor to degrade the quality of the article. Therefore, generally, the mold is designed such that the gate mark appears at a location of the product where the gate mark is not noticeable. In the case of a barrel cylinder for a writing instrument, for example, an inner surface portion of the distal end port of the barrel cylinder where the writing element extends is preferable as the location where the gate mark appears, because the gate mark formed at this location is not easily seen from the outside. However, since the distal end port of the barrel cylinder supports the distal end portion of the writing element so as not to move undesirably and smoothly guides the writing element when the writing element is extended/retracted, the size precision of the distal end port of the barrel cylinder must be increased such that the inner diameter of the distal end port of the barrel cylinder is slightly larger than the outer diameter of the writing element. If a gate mark appears on the inner surface portion of the distal end port of the barrel cylinder, it is difficult to obtain desired size precision.